The invention relates to a method and an apparatus for the manufacture of padding material, particularly for packaging purposes, as well as a corresponding padding material.
In many fields of the trade in goods, e.g. in production enterprises, in commerce or for final consumers frequently packagings arise in large quantities and are usually disposed of unused following the removal of the goods, Packagings made from inherently rigid flat material such as cardboard, corrugated board, board or the like are generally torn for this purpose or broken into small pieces in some other way and after collection serve as waste paper.
Not inconsiderable labour and other cost arise in the case of disposal in accordance with regulations.
A further problem in the packaging sector occurs with padding materials, which are used in the packing of products sensitive to mechanical actions, so as to protect said products, e.g. during transportation against impacts and similar effects. Frequently use is made of plastic chips as padding material and they give rise to considerable costs both during manufacture and disposal and are prejudicial to the environment if not correctly disposed of.
The object of the invention is to propose improvements in the packaging sector.
According to the method of the invention a padding material more particularly suitable for packaging purposes is manufactured from inherently rigid flat material, such as cardboard, board, etc., in that the flat material is so partially separated into strip sections, that in the transverse direction of the strips neighbouring strip sections remain interconnected by spaced connecting areas and in that the strip sections are so deformed in a direction at right angles to a neutral face of the flat material between the connecting areas that in the transverse direction adjacent strip sections are deflected in opposite directions.
As a result of the inventive shaping of the flat material with respect to the starting flat material a disposal problem may be solved and as a result of the resulting padding material a manufacturing problem is solved. An inherently prejudicial, namely superfluous starting material, such as cardboard packaging is not disposed of in an expensive manner and is instead appropriately transformed directly for reuse. From the substantially two-dimensional flat material, which can e.g. have a thickness between approximately 0.5 and approximately 5 mm and which is only generally slightly compressible perpendicular to the surface extension, as a result of the shaping according to the invention a padding material with a substantially three-dimensional structure is created and now the material xe2x80x9cthicknessxe2x80x9d determined by the enveloping surface of the deformed material can be a multiple of the starting thickness and a shock-absorbing resilience is created in the vicinity of the deflected strip sections. Through the separation into longitudinal strips the padding material is readily flexible in the transverse direction, so that it can e.g. be eminently placed around the bottle contour for packing bottles. A bending and/or compression of the structure comprising connected strips is also possible in the longitudinal direction. The padding effect is essentially produced in the vicinity of the oppositely deflected strip sections which, following separation and deformation, are substantially permanently deflected and are frictionally held in shape by edge friction. Improvements in retaining the deflection can be obtained in that the cut is made slightly frayed or toothed. This can be achieved by correspondingly manufactured cutting disks of the apparatus.
Although it is possible to deflect several adjacent strips as a group in one direction and a following group or an individual strip in the opposite direction, preferably individual strip sections are alternately deflected in opposite directions, so that a particularly good padding action is obtained.
The open, three-dimensional padding material structure can e.g. be produced by a punching process, in which the shaping substantially takes place simultaneously over a larger and in particular the entire surface of the starting material. Preference is given a separation by strip cutting with a cutting direction parallel to the neutral face of the flat material and for producing the connecting sections strip cutting is zonally interrupted. This permits the shaping of the starting material in energy-saving manner in a continuously progressing process and for producing larger area padding material parts use can be made of relatively small cutting devices which can be set up in space-saving manner. For padding material production it is possible to use appropriately modified document shredders or the like designed for strip cutting.
A particularly advantageous material structure can be obtained in a further development in that groups of e.g. three transversely adjacent connecting areas are in each case separated from one another in the transverse direction. This makes it possible to improve the flexibility of the padding material in the longitudinal direction, i.e. with a curvature about a transverse direction-parallel axis, because in the separating area it is possible to obtain an opposing movement of the groups of strips in each case connected at the connecting areas. This also creates a reversible extensibility of the material in the transverse direction.
The padding material made possible by the invention can exclusively comprise the inherently rigid starting flat material, because in padding material production it is not necessary to add new substances such as adhesives or the like or to work at temperatures or environmental conditions where possibly unfavourable changes could occur. Suitable starting materials are in particular packaging materials such as stiff paper, fine board, cardboard or corrugated board, the materials being in single or multiple layer form. Typical starting thicknesses are between approximately 0.5 and approximately 5 mm, but in exceptional cases can be larger or smaller. Typical padding material thicknesses can be approximately twice to five times the starting material thickness and/or between approximately 1 mm and approximately 25 to 30 mm. Particularly suitable strip widths of the normally substantially parallel side-bounded strip sections can be between approximately 0.5 and 4 times the flat material thickness, particularly between once and twice said starting thickness. Such relatively compact cross-sections are particularly shape-retaining and damping-aiding.
The average strip length between successive connecting areas can be more than 5 times, preferably between 20 and 40 times as large as the flat material thickness and/or between approximately ca. 3 and approximately 20 times, particularly between approximately 10 and approximately 15 times as large as the strip width. This makes it possible to obtain a good compromise between the padding material thickness co-determined by the free strip length and the damping or absorbing action. It must be borne in mind that experience has shown that the padding action decreases as the strip length increases.
Through the use, made possible by the invention, of substantially two-dimensional, inherently rigid flat or packaging material for the production of substantially three-dimensional, shock-absorbing padding material not only is the disposal problem solved with respect to the not further usable cardboard packaging or the like, but also inexpensively producible padding material is provided, which can optionally be used several times and if a further use is not necessary or desired, can be returned in environmentally friendly manner to the disposal cycles already established for packaging materials. It is obviously possible to use as the starting material flat material which has previously been used for another purpose.
An apparatus for the manufacture of padding material particularly suitable for performing the described method is based on the principle of the known document or data shredder. It has a cutting mechanism with two cooperating, oppositely drivable cutting rollers, whereof each has a plurality of cutting disks, which are axially bounded by cutting edges and between which there are axial gaps, in which in each case engage the cutting disks of the other cutting roller in an overlap area up to a maximum overlap depth for the purpose of producing a cutting engagement. In apparatuses according to the invention the cutting rollers are constructed in such a way that the cutting engagement between adjacent cutting disks is interrupted at least once during a revolution or cycle. Thus, during a normally preponderant part of the cycle a strip cut is produced in the manner of the known strip cutter-document shredder, but during the interruption of the cutting engagement a linking bridge remains between directly adjacent strips. The deformation of adjacent strip sections in opposite directions is achieved without further working steps in that the flat material strips are pressed by the cutting disks into the facing gaps or recesses of the in each case other cutting roller.
A further development is particularly advantageous in which the cutting disks preferably have circular circumferential surfaces, which are interrupted by at least one circumferential groove or marginal recess, the groove having a depth which is equal to or larger than the maximum overlap depth of cooperating cutting disks. Thus, outside the groove area in the vicinity of the cutting gap there is an overlap and therefore a separation of adjacent material areas, whereas in the overlap-free circumferential portion in the vicinity of the groove no cutting engagement occurs and correspondingly a bridge connecting the strip sections in the transverse direction remains. Its longitudinal extension is essentially determined by the circumferential length of the groove area, which is the same or less than the overlap depth. This circumferential length can e.g. be between approximately 2 and approximately 5% of the cutting disk circumferential length. According to a preferred further development the cutting disks have in each case two diametrically facing grooves and it is generally preferable if a cutting disk has a preferably even number of grooves regularly distributed about the cutting disk circumference, e.g. two, four, six or eight such grooves.
According to a further development, the cutting rollers are so mutually positioned that in an overlap area of cutting disks, at least for certain disks, alongside a groove of one cutting disk of one cutting roller is positioned a groove of a cutting disk of the other cutting roller. As a consequence thereof on rotating the cutting rollers on some axial cuts thereof the grooves of displaced facing cutting rollers meet. This makes it possible to attain for a uniform padding behaviour of the padding material a particularly preferred deformation substantially symmetrically to the starting material face. In the case of meeting grooves a cutting engagement is also avoided if each groove is flatter than the maximum overlap depth, provided that the sum of the groove depths exceeds the maximum overlap depth, so that in the cutting gap there is an internal spacing between the groove bases or bottoms.
It is particularly advantageous if grooves of adjacent cutting disks of a cutting roller are circumferentially displaced by an even-numbered fraction of 180xc2x0 with respect to one another, e.g. by 45, 60 or 90xc2x0. As a result of this displacement of the grooves, it is possible to ensure that the connecting areas of individual strips or strip groups, considered longitudinally, are alternately transversely, mutually displaced. As a result the cut padding material is readily flexible in the longitudinal and transverse directions and is reversibly extensible in the transverse direction.
To avoid an undesired crosscutting or tearing at the strip sections in the vicinity of the groove edges, according to a further development in the transition area between a groove and the circumferential surface of the cutting disk a chamfer and/or curvature is provided.
For ease of operation during material supply and padding material removal according to a preferred embodiment the cutting disks are superimposed, so that a supply of the generally planar flat material and a removal of the padding material produced can take place horizontally. In the case of a horizontal material throughput, it is e.g. particularly simple to have a suitable collecting and/or conveying mechanism or the like following the material outlet.
A method particularly useful for operating the driving electric motor of the cutting mechanism of the cutting mechanism of the described apparatus is characterized in that an at least single phase alternating current is generated from a direct current, particularly of arbitrary origin by conversion and is used to supply the electric motor.
Devices for constructively similar document shredders frequently have so-called universal motors, whose special construction also permits operation with a.c. voltage. For applications such as in the office sector, they are normally operated with the standard a.c. voltage of the building (230 volt, single phase). Disadvantages of universal motors caused by their construction such as wear and radio-interference problems are partly avoided through the use of three-phase asynchronous motors, e.g. squirrel cage motors. However, it is necessary to install for these separate three-phase current connections or terminals, which often involves high costs, more particularly in the office sector.
In other solutions the rotary field is generated by means of a phase-displaced magnetic field. The necessary phase displacement is brought about by the series connection of a capacitor, so as to operate therewith a single-phase motor. However, due to the high ohmic losses in the rotor and the high no-load current, the power characteristics of such drives are not particularly good. The power roughly corresponds to 65% of that of a comparable three-phase motor.
By the invention of the method for the driving electric motor with the features of claim 16 a method can be provided with which the drawbacks of the prior art can be avoided enabling a document shredder electric motor to be operated at a higher power level, so as in particular to permit connection to numerous supply terminals.
On the basis of the direct current a considerable design scope is obtained for the generation of the at least single-phase alternating current. Preferably three-phase alternating current, i.e. three-phase current is generated. The direct current can be converted into a variable frequency alternating current permitting an adaptation to the in each case required operating state of the electric motor. Preferably in the case of a Limited electric motor loading in operation a high frequency is set, so that particularly when using squirrel cage motors there is a higher speed and consequently a faster document shredding. It is possible to provide several fixed speeds with which it is possible to set different speeds (slow, medium, fast) for different operating modes. Further advantages, particularly on starting the electric motor, can be obtained through a continuous changing of the frequency and therefore the speed. Wear to the complete apparatus can be reduced by the avoidance of suddenly occurring peak loads or jerky speed changes. In addition, operating comfort is increased.
Special advantages of this method for devices for manufacturing padding material can be seen, amongst others, in that professional, efficient and robust rotary current motors become available for office uses without rotary current terminals. Advantages of rotary current motors also can be seen in low noise generation, which in turn is advantageous in office uses.
In particular a very good controllability of the rotary current machine is achieved by changing the frequency of the output rotary current at the inverter. Therewith thin card material can be worked very fast and thick or even very thick material can be worked with lower speed and very high torque. This allows to generate the respectively needed padding material from starting materials with various thicknesses according to individual needs, so that a storage of ready padding material becomes obsolete.
The starting material, in turn, is much more space saving than the padding material. Thanks to the invention it is possible, for the first time, to obtain these advantages using a device suitable for office use.
In addition, the amplitude of the a.c. voltage can be variable for adapting to the electric motor operating behaviour required by any particular user. Preferably the alternating current generated is sinusoidal and as a result of the power electronics of the converter it is also possible to produce other and in particular random shapes or wave shapes.
It is possible to obtain the direct current from a fixed installed direct current network and optionally from an emergency power supply. The direct current is preferably produced from a random alternating current supply, particularly a single-phase alternating current supply. Thus, a desired, e.g. three-phase alternating current can be generated by means of the direct current intermediate circuit from a normal 230 volt connection. With such a procedure a document shredder with a three-phase motor can be operated on a normal socket. Further advantages arising on converting an alternating current by means of a direct current intermediate circuit into an alternating current supply for the electric motor are the extensive, random adjustability of the frequency, amplitude and shape of the alternating current produced. Detailed explanations are given hereinafter in connection with the description relative to the drawings.
According to a possible method of the invention, the alternating current for the electric motor can be generated from the direct current by an inverter as the first converter, in which the inverter is preferably connected by means of an intermediate circuit to a rectifier as the second converter for generating the direct current from the mains voltage. The converters are preferably power electronics assemblies, e.g. equipped with triacs, power transistors or thyristors as valves. On the one hand the converters can be interconnected by means of a type of buffer and on the other it is possible to directly interconnect them, optionally via a direct current intermediate circuit. The inverter is constructed as a function of the alternating current to be generated and generally with six valves for generating the three-phase current.
An apparatus according to the invention for the operation of an electric motor of a document shredder for shredding flat material, which is advantageously suitable for the performance of the above-described method, has at least one converter, which generates an alternating current with at least one phase for the electric motor from a direct current. The converter operates as an inverter and preferably generates three-phase current. Advantageously a three-phase motor or asynchronous motor is used. An asynchronous motor with a squirrel-cage rotor is particularly advantageous for operation on a three-phase alternating current. By means of a converter with power electronics it is possible to generate an alternating current with a substantially random shape. Apart from the aforementioned inverter as the first converter it is possible to provide a rectifier as the second converter and this makes it possible to generate the direct current from an alternating current supply. This can e.g. be single-phase, e.g. in the form of a standard socket installed in a home or office. The second converter can be connected by means of a variably constructed intermediate circuit to the first converter. An adjustment of the frequency of the first investor for changing the votation speed of the motor an be manually operable, for instance for an increase of the frequency by a factor of at least three up to ten maximum.
It is also possible to provide on the electric motor a tachometer, particularly on one of its shaft ends for regulating at least one of the converters as a function of the load situation and/or the position of the motor shaft. Load sensing can take place by means of a tachometer, a current detection or any suitable sensor means. This is advantageously used for controlling the first converter. These and further features can be gathered from the claims, description and drawings and the individual features, both singly or in the form of sub-combinations, can be implemented in an embodiment of the invention and in other fields and can represent advantageous constructions for which protection is hereby claimed.